Process of purifying alkali stannates.



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' UNITED- sTA -ns PATENT OFFgCE GUSTAV SPITZ, OF BRT j'NN, AUSTRIA-HUNGARY, ASSIGNOR T0 GOLDSCHIVLIDT DETILN- NING COMPANY, OF NEW YORK, N. Y., ;A CORPORATION OF NEVT J PROCESS OF PUBIFYING ALKALI STANNATES.

To all whom'it may concemr ject of the Emperor. of AustriaI-Iungary, and resident of-Briinn, in the Empire of Austria-Hungany,11aire invented a new and nates, of which the following is an exact description.

Myfinvention consists in a process for cleaning solutions of alkali, which have been used for the purpose of separating metals from metal coated waste and which contain such anamount of impurities that they are no longer able to separate the metal.

During the process for separating metals,

' which are soluble in alkalis, from ,metal waste, alloys, etc., ,by treating the latter under pressure with fa hot alkaline solution containing an excess of-v free alkali" and oxidizing means, there will be obtained at the end of the operation a lye which still contains a small percentage of free alkali. 'Thislyehas been made use of by adding a fresh alkaline solution so that the solution was again fit to act upon' metallic material. I have described such a process in my co-pending application #526603,

in the following-manner, choosing as an exfiledNov. 6, 1909 Npw, I have found that' the dissolving action of the solution is considerably reduced by the various impurities with which it is contaminatedduring thecourse of the operation. Thus, for instance,-during, the'proce'ss of detinning tinplate scrap, the solution is. contaminated with silica, alumina and lead. These contaminations not only reducethe dissolving action of the solution but they will, of course, also contaminate the product to be obtained, in this case, the oxid of tin. In order to avoid these drawbacks, I proceed ample the treatment of tin bearing material. Into the solution obtained at the endof the above-mentioned process, tin-bearing ma terial, as for mstance tin scrap, is placed,

without adding a fresh amount of alkaline I Specification of Letters Patent. Application filed November (L 1909. x Serial No. 526,604.

of free alkali or less, there will be produced Patented Oct. 22, 1912.

only oxid of tin which is not dissolved by the small amount of free alkali present in the "solution. .This oxid of tin, at the mouseful Process of Purifying Alkali Stan- "The solution ofstannate ofsqdium freed from this precipitate is considerably cleaner than that obtained by treating.'thetin-bear.

posible'to obtain heretofore.

\Vhat. I claim is:

1. Process of purifying an impurealkaline solution of alkali .stannate containing impurities such as silica, alumina and lead,

ment yof its being produced, carries with .itselfthe greatest part of the impurities, as for instance silica, alumina and lead, which are thus precipitated in an insoluble condition. i

which process consists in treating the solution with material containing metallic tin in the presence of an oxidizing salt.

2. Process of purifying an" impure alkaline solution of alkali stannate containing impurities such as silica, alumina and lead,

.which process consists in treating the solution with material containing metallic tin in the presence of sodium nitrate. I

3. Process of purifying an impure alkaline solution of alkali stannate containing impurities such as silica, alumina and lead,

which process consists in adding to the so-' lution tin scrap'in the presenc'e'of an oxidizing salt.

4. Process of purifying an impure alkaline solution of. alkali stannatev containing impurities such as silica, alumina and lead, which process consists in adding to the solution tin scrap in the presence of sodium nitrate. 1 I

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

GUSTAV sPrr'z.

Witnesses AUGUST FUcsER, A LEXANDER 3v EINGARTNEB.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. .W fiee 210" 

